Matrix please help stressing!

hey there i know it was a while ago but your answer seems clear any chance you know how to get the invertible and diagonal of a 3x3 matrix?? i've got the two eigenvalues and eigenvectors already!!!!

(just incase you need to know)

eigenvalues being 2 and -3

eigenvectors being (-1 over 3 over 1) for 2 and the second one is (1 over -1 over 2) for -3!

the matrix is a 3x3 its(3 4 -1

-1 -2 1

3 9 0)

dunno do you need to know but i said id write it anyway thanks a lot!!!!!!11